The Black Hills are very cool, but I would be hesitant to do them on a bike. The reason is that you have a lot of narrow mountain roads and old people in RVs.

Great place for mountain biking but it can get damn hot and I'm sure the road riding is great as well but have never actually been there for that. Check Strava for routes - having lived in a few touristy areas, do what you can to make sure all the gapers see you especially if you're there during the peak season.

Have a CX/gravel bike? This course looks outstanding:
http://www.goldrushgravelgrinder.com/

Google Black Hills Road Maps. It'll give you an overview of the roads and some of the gravel roads.

I've ridden a lot in the Black Hills. I wouldn't say there are killer climbs (that's relative as I live in CO) but there are plenty of climbs and constantly rolling hills. My favorite rides have been mixed road and gravel rides. The Black Hills have a ton of gravel roads. The Mickelson Trail is a gravel path that runs North/South throughout the Hills.

I've ridden on both Memorial Day and July 4th weekends and didn't find the traffic bad at all. Later in July and early August is another story as that coincides with Sturgis.

My in laws used to live in Hot Springs at the south edge of the Hills and I'd usually ride from there.

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Formerly DrD

It's been a while since I lived there but once upon a time Tim at Acme Bikes was the go to for Black Hills riding wisdom.

There are plenty of good roads to ride but I preferred the southern hills for road bikes. Some of my favorites are Iron Mountain rd, Needles hwy, Sheridan Lake rd, Neck Yolk. Most of the roads are alright for bikes but be careful on 385 which can get busy.

If you have a chance to ride off road the single track is fantastic. The Centennial trail is fantastic, Storm Mountain is fun, the Rim Rock trails by Hisega are great. Up north the Tinton trail has great flow and well maintained for the Dakota 50.

So do you have a timeframe in mind? I live in Rapid City and ride the Black Hills roads all the time. I would be happy to take you out on some of our group rides, time trial, or just casual ride with a couple of us. As for climbs, we have Lots of options depending on how much you want - no it's not Colorado but we can usually get well over 3k vertical in over a 2 1/2 ride. The summer does get more congested with tourists particularly around Custer State Park and Mt Rushmore, but we have routes that easily avoid most of the heavy traffic or can get out early enough to avoid it. Although you will want to avoid early August as the Sturgis Rally is usually the first full week but about a half million bikers show up and take over the entire region. Send me a PM if you have more interest and want to chat.

Tried the black hills two years ago and was a bit sketchy with RV traffic. Had to ride early in the am and be done by 10am.

I tried Phoenix two months ago and it was a bit sketchy with 98 degree temps. Had to ride at 7 am and be done by 10am.

Funny---I have sales reps and managers who report to me who work in SD and was thinking the same thing.....Be curious to follow this thread.